The present invention relates to a desoldering unit for removing an electronic element from a circuit board by melting solder surrounded the electronic element, and more particularly to a photothermic desoldering unit that employs the effect of light and heat to provide even desoldering temperature to melt solder for removal of an electronic element from a circuit board without damaging the circuit board and other adjourning electronic elements.
A desoldering unit is particularly designed for melting solder surrounded electronic elements soldered onto a circuit board, so that the electronic elements may be removed from the circuit board for replacement or repair. Currently, there are three types of desoldering apparatus frequently employed in the electronic industrial field, namely, hot-air blower, BGA (Ball Grid Array) Rework Station, and compact desoldering heater.
The hot-air blower produces hot air and blows the same directly toward a target electronic element that is to be removed from a circuit board (see the attached reference document), so that solder surrounded the target electronic element is molten to release the electronic element from the circuit board. Thereafter, a vacuum suction tube is used to suck the released electronic element to move it from the circuit board. Since hot air from the hot-air blower not only blows toward the target electronic element to be removed but also areas on the circuit board in vicinity of the target electronic element, the hot-air blower is only suitable for desoldering electronic elements fixed on the circuit board of a surface mount device (SMD). Since it is uneasy to control a distance between the blower and the target electronic element to be removed and the temperature of hot air used to melt the solder surrounded the target electronic element, areas on the circuit board adjacent to the target electronic element tend to be heated, softened and deformed and could no longer be utilized normally.
The BGA Rework Station is a unit designed for professional use and is very expensive (see the attached reference document). It also employs the physical principle of hot air and therefore has the same disadvantages as the hot-air blower, such as uneven distribution of hot air over the circuit board and the target electronic element, undesired damage of adjourning electronic elements on the same circuit board, etc. Moreover, the BGA Rework Station is only suitable for electronic elements on electronic devices using BGA type package that represents connection of electronic elements only to the surface of a circuit board.
An example of the compact desoldering heater is shown in FIGS. 1 and 2. As shown, the compact desoldering heater mainly includes a console 1 on which a switch 11 and a temperature control knob 12 are provided, and a heating element 13 horizontally mounted on a top of the console 1. A surface temperature of the heating element 13 is controlled through the switch 11 and the temperature control knob 12. To use the compact desoldering heater to melt solder and remove an electronic element 21 from a circuit board 2, the circuit board 2 is positioned directly on the heating element 13 with pins 22 projected from a bottom surface of the electronic element 21 immediately on a top surface of the heating element 13. Heat from the heating element 13 melts solder surrounded the pins 22 to achieve the purpose of removing the target electronic element 21 from the circuit board 2. Such compact desoldering heater melts the solder by directly contacting with and heating the solder and is only suitable for contacting with a rear side of the circuit board 2. More specifically, the compact desoldering heater is only applicable for electronic elements on electronic devices using Dual In-line Package (DIP) in which pins are downward extended through the circuit board.
In view that the above-mentioned conventional desoldering apparatus have their respective disadvantages and each of them could be applied to desolder and remove electronic element limited to only one single type of package, it is desirable to develop a universal desoldering unit that eliminates problems existing in the conventional desoldering apparatus, such as uneasily controlled eating temperature, softened and deformed adjourning areas on the circuit board, damaged adjacent electronic elements on the same circuit board, and could be used to desolder and remove electronic elements from circuit boards of electronic device of all kinds of packaging types, including SMD, BGA, and DIP types of packaging.